in reply to Memory is not released back to operating system

To be absolutely sure your memory gets released back when you want, fork the code off. See Re: undefining hashes to free memory for more info on non-forked problems with memory. Otherwise, the Perl interpreter will greedily hang on to the memory, figuring if you used it once, you probably will want to use it again.

I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku ................... flash japh